The body ecu (Mem's) is very complicated. It's the active anti theft system ie the alarm it handles all sorts like windows, how long the interior light stays on and hundreds more functions that you don't need.

I would make or buy a simple car loom and add the engine loom as a stand alone package just like an omex, ms, dta ( insert any brand you like here).

Down side. It's more complicated than the above. And it's not viable to tune it much.

Up side. No mapping needed and it starts on the button. It will meet current mot emissions providing you use all the bits needed and it's very very cheap.

Where do I come in. Give me a shout if you go this way and need help.